Are we sure that anyone would really want to do that(You will see what I mean)?
Here are some of my favorite characters in no particular order.
Onizuka (GTO) : Do you really want a weird perverted man like him following you around(especially if you are a female)? I mean sure he can teach you how to be a good person and beat up people for you but he would be trouble too.
Vash The Stampede (Trigun) : Sure Vash is a great guy and he cares about the people around him but if he was pissed off he could blow up a city not mention he has a bounty on his head so trouble would follow him.
Kaolla Su (Love Hina) : Cute but weird foreign little girl. The whole tranformation in a full moon thing is cool to see the older version of her but um she could beat you up. On second thought Naru is a better choice but she could beat you up too.
Excel Excel (Excel Saga) : Annoyingly funny teenager girl who talks really fast and wants to take over the world. I would lose my sanity if I was stuck with her for five minutes. Maybe Hyatt would be a better choice but the whole dying thing would creep me out.
Now do you see that sometimes it's just better to pick an anime or manga instead of having your favorite character in the real world. That was very fun yea!